Fuel is a huge part of the performance of your vehicle, and is
unfortunately one of the least considered aspects of it’s running. The casual motorist
takes gas for granted. Its ubiquitous, pretty similarly priced, and sometimes
just another chore that is part of vehicle ownership, right?

Wrong. No matter how well engineered your vehicle is, to keep it
running well proper maintenance and the right type of gasoline are essential.
Unleaded gas is classified according to octane rating. In the US we have
87 (regular) 88-90 (mid) and 91-94 (performance). Often, they are not all
available at one specific gas station.

So, what exactly does this rating mean? Will you damage your auto
by mixing 87 with 92 octane? Which number is the best for you? In this article
we’ll answer those questions and more.

Octane Rating Explained

Octane rating refers to the percentage of an organic molecule
called iso-octane that is commonly found
in gas. This one molecule is fairly important as it regulates the controlled
burning of the fuel in your engine.

How does It Work?

In the internal combustion cycle the air and fuel mixture is
compressed inside the cylinder and then ignited by the spark plug at a very
critical position so as to maximize the torque transmitted to the crankshaft.
This assumes though that the fuel air mixture only ignites on the spark from
the sparkplug.

What’s That Knocking Sound?

Sometimes things can get a little ahead of themselves and the mixture spontaneously ignites before the spark. Of course, this would be at the wrong time for what the engine requires, and the result is a pinging noise or engine knock. Usually this does not damage the engine, as it is designed to tolerate it happening, but prolonged knocking cycles can completely destroy the pistons and other mechanical parts of the engine which can lead to a costly rebuild. That is where iso-octane comes in. Basically, the higher the concentration of iso-octane in gas, the more pressure it can withstand without spontaneously igniting and causing an engine knock. This is essential for almost all performance engines which use much higher compression ratios then your vanilla daily drivers.

Fortunately, modern cars are largely computer controlled, and
designers have included a clever knock sensing system. This detects the uneven
vibrations that occur when knocking happens and decreases cylinder pressure or
retards the spark timing to compensate for the knock. This does tend to reduce
your engine performance.

Which Octane Rating Is Right For Me?

The type of gas
you should use largely depends on what you are planning on doing with your auto.
Some of us only have one car that is the daily during the week and gets opened
up on weekends to get the blood flowing. In that case, you’d want to stick
somewhere in the midrange of 88-90 research octane number (RON). If you’re only
using the car for street or track stuff, then the premium range is best for
you, but as a daily driver only, it will suit your wallet better to stick with
the lower octane ratings. It’s not the best practice to mix two different
ratings of gas, but if you have to, your vehicle will be able to compensate for
it, but rather try to add a higher octane gas to a lower one if possible. Also
remember that not all gas stations are created equal; try to go to one that is
always busy – that way you can be assured of getting gas that hasn’t sat around
in the underground storage tanks for too long.

If you’re still unsure of what type of gas is best for you, why
not look at what your manufacturer recommends? Alternatively pop into our Pompano Beach automotive shop, Foreign
Affairs Motorsport for friendly advice. You don’t even need to knock.